Thunar can be funny like that sometimes. Thunar can have problems with deleting files if there is more than one file in the trash with the same name or if there is a . hidden/configuration file in the trash.

If you can see the files that are not being deleted when you go to your trash bin you can use the Shift + Del combo to try to make them go or if they still won't go you can try restoring the offending items and then use Shift + Del on those files to bypass the trash can altogether.

If you can't see the offending files then click on View > Show Hidden Files to see if a . file was deleted. You can then use the above method to get rid of the files or restore them if you didn't mean to delete them.

Lastly it could possibly be a bug that was in Thunar some time ago. I don't know if this pertains to Vector's 7.0 (I am currently using Fedora so I don't know what version of Thunar is in 7.0) but Thunar did have a bug where certain deleted files would have the permissions changed as they were moved to the trash. In this case you need to get into your users home trash by way of root, so open Thunar with sudo and go to /home/YOUR-USER-NAME/.local/share/Trash/files. You should then be able to delete the problem files.

Hope this helps and please post back if you are still having problems.